reserve y for set,
  x,r,a,b for Real,
  n for Element of NAT,
  Z for open Subset of REAL,
  f,f1,f2,f3 for PartFunc of REAL,REAL;

theorem Th3:
  x>0 implies x #R (-1/2)=1/sqrt x
proof
  assume
A1: x>0;
  hence x #R (-1/2)=1 / x #R (1/2) by PREPOWER:76
    .=1 / sqrt x by A1,Th2;
end;
